The present invention generally relates to an image forming apparatus such as a laser printer, a copying machine, or the like, for forming an image onto a recording medium, and particularly relates to an image forming apparatus having a plurality of paper supply portions.
A laser printer in which high printing quality is provided is frequently used as an apparatus for printing a document, a chart, or the like, formed by means of an information processor such as a word processor or the like. Further, the formed document or the like is easily copied by using an ordinary electrostatic copying machine.
In each of the laser printer and the copying machine, a photoreceptor drum, a photoreceptor belt, or the like is generally used and an image is formed by transferring a toner image formed on the surface of the photoreceptor body onto recording paper. Generally, such an apparatus has a plurality of paper supply portions, and in order to transfer a toner image on the photoreceptor body onto recording paper at a suitable position, it is necessary to accurately control the timing of transfer. For this, there has been proposed such a following paper supply device as disclosed, for example, in Japanese Patent Unexamined Publication No. Sho. 60-56751.
The paper supply device has such a configuration that a pair of rolls called aligning rolls (hereinafter, referred to as "resist rolls") are provided between paper supply rolls (herein after, referred to as "feed rolls") and a photoreceptor drum so that recording paper fed by the feed rolls is made to hit against the resist rolls so as to stop once, and then the recording paper is fed to the photoreceptor drum by restarting drive of the resist rolls in predetermined timing. That is, a stand-by position of a front end of recording paper is limited by the resist rolls.
In the conventional apparatus, the timing of transfer of an toner image on the photoreceptor drum onto recording paper is adjusted by the resist rolls against which recording paper hits so as to become into a stand-by state as described above. Therefore, existence of the resist rolls is a large obstacle in miniaturizing the apparatus.